# 6 Lecture

## PHY101

### Midterm & Final Term Short Notes

## Applications of Newton’s Laws – II

Newton's laws of motion, which describe the relationship between force, mass, and motion, have numerous practical applications in everyday life.

**Important Mcq's**

Midterm & Finalterm Prepration

Past papers included

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**A 10 kg object is placed on a surface with a coefficient of static friction of 0.4. What is the maximum force that can be applied to the object before it begins to move?**

A. 4 N

B. 40 N

C. 100 N

D. 400 N

Answer: B. 40 N

**A 2 kg object is accelerating at a rate of 5 m/s^2. What is the net force acting on the object?**

A. 0.4 N

B. 2.5 N

C. 5 N

D. 10 N

Answer: D. 10 N

**A 1000 kg car is traveling at a speed of 20 m/s. If the brakes are applied and the car comes to a stop in 5 seconds, what is the average force exerted on the car by the brakes?**

A. 4000 N

B. 8000 N

C. 10000 N

D. 20000 N

Answer: C. 10000 N

**An object with a mass of 5 kg is suspended from the ceiling by a rope. What is the tension in the rope?**

A. 5 N

B. 9.8 N

C. 49 N

D. 50 N

Answer: B. 9.8 N

**A 20 kg object is sliding down a frictionless incline with an acceleration of 2 m/s^2. What is the angle of the incline?**

**A. 11.3 degrees**

B. 22.6 degrees

C. 30 degrees

D. 45 degrees

Answer: B. 22.6 degrees

**A 5 N force is applied to an object with a mass of 2 kg. What is the acceleration of the object?**

A. 0.4 m/s^2

B. 2.5 m/s^2

C. 5 m/s^2

D. 10 m/s^2

Answer: D. 10 m/s^2

**An object with a mass of 10 kg is on a surface with a coefficient of kinetic friction of 0.3. If a force of 50 N is applied to the object, what is its acceleration?**

A. 1 m/s^2

B. 2 m/s^2

C. 3 m/s^2

D. 5 m/s^2

Answer: A. 1 m/s^2

**A 1 kg object is traveling at a speed of 10 m/s. What force is required to bring the object to a stop in 5 seconds?**

A. 2 N

B. 10 N

C. 20 N

D. 50 N

Answer: C. 20 N

**An object with a mass of 2 kg is pushed with a force of 10 N. What is the acceleration of the object?**

A. 2.5 m/s^2

B. 5 m/s^2

C. 10 m/s^2

D. 20 m/s^2

Answer: B. 5 m/s^2

**An object with a mass of 10 kg is traveling at a speed of 5 m/s. What force is required to double the object’s speed in 5 seconds?**

A. 5 N

B. 10 N

C. 25 N

D. 50 N

Answer: D. 50 N

**Subjective Short Notes**

Midterm & Finalterm Prepration

Past papers included

Download PDF
**Explain the concept of terminal velocity.**

**Answer: **Terminal velocity is the maximum velocity that an object can achieve when falling through a fluid, such as air or water. As the object falls, the fluid resistance increases, slowing down its acceleration until the upward force due to the fluid resistance equals the downward force due to gravity. At this point, the net force acting on the object becomes zero, and the object continues to fall at a constant velocity, known as the terminal velocity.

**What is the difference between static and kinetic friction?**

**Answer: **Static friction is the force that resists the motion of an object at rest, while kinetic friction is the force that opposes the motion of an object in motion. Static friction is generally greater than kinetic friction, and it must be overcome to set an object in motion.

**Can an object be in equilibrium if it is accelerating?**

**Answer:** No, an object cannot be in equilibrium if it is accelerating. Equilibrium means that the net force acting on an object is zero, which means that the object is either at rest or moving at a constant velocity. If an object is accelerating, then the net force acting on it is not zero, and it is not in equilibrium.

**Explain the concept of tension force.**

**Answer: **Tension force is the force that is transmitted through a string, rope, cable or wire when it is pulled tight by forces acting on either end. It acts in the direction of the string, pulling the object in that direction. Tension force can be found in many situations, such as when lifting an object with a crane or pulling an object with a pulley.

**What is the relationship between mass and weight?**

**Answer: **Mass is a measure of the amount of matter in an object, while weight is a measure of the force of gravity acting on an object. The weight of an object is equal to its mass multiplied by the acceleration due to gravity. Therefore, the weight of an object will vary depending on the strength of the gravitational field it is in, while its mass will remain constant.

**How does air resistance affect the motion of an object?**

**Answer: **Air resistance is a force that opposes the motion of an object through the air. It increases as the speed of the object increases and can eventually become equal in magnitude to the force of gravity, causing the object to reach its terminal velocity. Air resistance can also affect the trajectory of an object, causing it to deviate from its expected path.

**What is the difference between elastic and inelastic collisions?**

**Answer:** In an elastic collision, the total kinetic energy of the objects involved is conserved, meaning that no energy is lost to other forms, such as heat or sound. In an inelastic collision, some or all of the kinetic energy is lost to other forms of energy. The objects may stick together after the collision, and the final velocity of the objects may be different from their initial velocities.

**What is impulse and how is it related to force and time?**

**Answer:** Impulse is the product of force and time and is equal to the change in momentum of an object. It is related to force and time because a greater force acting for a longer period of time will produce a greater change in momentum, and therefore a greater impulse.

**What is the law of action and reaction?**

**Answer: **The law of action and reaction, also known as Newton's third law, states that for every action, there is an equal and opposite reaction. This means that when one object exerts a force on another object, the second object will exert an equal and opposite force back on the first object.

**How does friction affect the motion of an object on an inclined plane?**

**Answer:** Friction opposes the motion of an object on an inclined plane

### Applications of Newton’s Laws – II

Newton's laws of motion, which describe the relationship between force, mass, and motion, have numerous practical applications in everyday life. In the first part of this article, we discussed the applications of Newton's laws in various fields such as transportation, sports, and aerospace. In this article, we will explore some more applications of Newton's laws.**Elevators:**Newton's second law of motion is the foundation for the design and operation of elevators. When an elevator is at rest, the force of gravity acting on it is balanced by the normal force of the floor. When the elevator starts moving upward, the force applied by the elevator motor is greater than the force of gravity, causing an acceleration in the upward direction. Similarly, when the elevator stops, the force applied by the motor decreases to balance the force of gravity, resulting in deceleration. The mass of the elevator, along with the applied force, determines the acceleration.

**Airbags:**Airbags in cars are designed to protect passengers during a collision by reducing the force of impact. When a car collides with an object, the passengers' bodies will continue to move forward at the same speed as the car until they are stopped by the seatbelt. However, their heads will continue to move forward due to the inertia of the head. This sudden change in motion can cause severe injuries. Airbags are designed to inflate in a fraction of a second during a collision, reducing the force of impact on the passengers' heads.

**Crumple zones:**Similar to airbags, crumple zones in cars are designed to absorb the impact energy during a collision. Crumple zones are areas of a car's body that are designed to deform in a controlled manner during a collision. This deformation absorbs the kinetic energy of the collision and reduces the force experienced by the passengers.

**Roller coasters:**Roller coasters are designed to provide an exhilarating ride while ensuring the safety of passengers. The principles of Newton's laws are applied to design the tracks, the train, and the speed of the roller coaster. The train's motion is controlled by the forces of gravity and the track's shape. The train is designed to maintain a minimum speed to ensure that it reaches the top of the next hill without slowing down due to friction.

**Projectile motion:**Projectile motion is the motion of an object that is launched into the air and follows a parabolic path under the influence of gravity. The motion of projectiles, such as cannonballs or baseballs, can be analyzed using the principles of Newton's laws. The force of gravity acting on the projectile causes a constant acceleration in the downward direction. The horizontal motion of the projectile is unaffected by gravity unless air resistance is taken into account.

**Swinging:**Swinging is a common pastime for children and adults alike. The motion of a swing can be analyzed using the principles of Newton's laws. The force of gravity acting on the person on the swing causes a downward acceleration. The force of tension in the ropes provides the necessary centripetal force to keep the person in a circular motion. The length of the ropes, the angle of the swing, and the person's weight all affect the speed and motion of the swing.

**Satellite orbits:**Satellites in orbit around the Earth follow a path determined by the forces acting on them. The gravitational force of the Earth causes a constant acceleration towards the center of the Earth. The velocity of the satellite must be sufficient to balance the gravitational force and maintain a stable orbit. The principles of Newton's laws are used to calculate the necessary velocity and altitude for a satellite to maintain a specific orbit.

**In conclusion,**the applications of Newton's laws are vast and varied, from transportation to safety devices to amusement park rides.